London's position as the best place for banking is under pressure
New York and London have been ranked as the joint-top global financial centres, according to research published by the City of London Corporation.
New York, which was previously second to London, was rated as a better place to do banking business than six months ago, while London's rating fell.
The City warned that "damage had been done" to London's competitiveness.
Bankers have previously warned that tougher regulation of UK banks could push the industry abroad.
Financial centres in Asia saw gains in their ratings, with Hong Kong, Singapore, and Shanghai all seen as improving places to do business.
The City of London Corporation's policy chairman Stuart Fraser said the gains of its rivals should be a "wake-up" for the UK.
"Although London and New York have always led the pack, this research is a wake-up call for decision-makers that our standing as a world-leading global financial centre should not be taken for granted," he said.
"Damage has been done to the Square Mile's perceived competitiveness relative to New York, but this is not irreversible."
Mr Fraser urged the next government to make a "positive statement" on their intentions for taxation and regulation of the UK's financial sector.